I am trying to add an additional domain controller using Windows 2019 Standard in a Windows 2012 R2 environment. As far as I can tell, this is supported by Microsoft.
When trying to promote the new server to a DC, I get an error that the wizard cannot gain access to the list of domains in the forest. The extra information states that the RPC server is unavailable. I have added temporary firewall rules to allow ALL inbound and outbound TCP and UDP traffic (just to see if I can get it to work), but that does not work.
I also verified many services are running on this machine as well as the "primary" domain controller.